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<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="boost_regex.syntax.basic_syntax"></a><a class="link" href="basic_syntax.html" title="POSIX Basic Regular Expression Syntax">POSIX Basic Regular
      Expression Syntax</a>
</h3></div></div></div>
<h4>
<a name="boost_regex.syntax.basic_syntax.h0"></a>
        <span class="phrase"><a name="boost_regex.syntax.basic_syntax.synopsis"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.synopsis">Synopsis</a>
      </h4>
<p>
        The POSIX-Basic regular expression syntax is used by the Unix utility <code class="computeroutput"><span class="identifier">sed</span></code>, and variations are used by <code class="computeroutput"><span class="identifier">grep</span></code> and <code class="computeroutput"><span class="identifier">emacs</span></code>.
        You can construct POSIX basic regular expressions in Boost.Regex by passing
        the flag <code class="computeroutput"><span class="identifier">basic</span></code> to the regex
        constructor (see <a class="link" href="../ref/syntax_option_type.html" title="syntax_option_type"><code class="computeroutput"><span class="identifier">syntax_option_type</span></code></a>), for example:
      </p>
<pre class="programlisting"><span class="comment">// e1 is a case sensitive POSIX-Basic expression:</span>
<span class="identifier">boost</span><span class="special">::</span><span class="identifier">regex</span> <span class="identifier">e1</span><span class="special">(</span><span class="identifier">my_expression</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">regex</span><span class="special">::</span><span class="identifier">basic</span><span class="special">);</span>
<span class="comment">// e2 a case insensitive POSIX-Basic expression:</span>
<span class="identifier">boost</span><span class="special">::</span><span class="identifier">regex</span> <span class="identifier">e2</span><span class="special">(</span><span class="identifier">my_expression</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">regex</span><span class="special">::</span><span class="identifier">basic</span><span class="special">|</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">regex</span><span class="special">::</span><span class="identifier">icase</span><span class="special">);</span>
</pre>
<a name="boost_regex.posix_basic"></a><h4>
<a name="boost_regex.syntax.basic_syntax.h1"></a>
        <span class="phrase"><a name="boost_regex.syntax.basic_syntax.posix_basic_syntax"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.posix_basic_syntax">POSIX
        Basic Syntax</a>
      </h4>
<p>
        In POSIX-Basic regular expressions, all characters are match themselves except
        for the following special characters:
      </p>
<pre class="programlisting">.[\*^$</pre>
<h5>
<a name="boost_regex.syntax.basic_syntax.h2"></a>
        <span class="phrase"><a name="boost_regex.syntax.basic_syntax.wildcard"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.wildcard">Wildcard:</a>
      </h5>
<p>
        The single character '.' when used outside of a character set will match
        any single character except:
      </p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
            The NULL character when the flag <code class="computeroutput"><span class="identifier">match_no_dot_null</span></code>
            is passed to the matching algorithms.
          </li>
<li class="listitem">
            The newline character when the flag <code class="computeroutput"><span class="identifier">match_not_dot_newline</span></code>
            is passed to the matching algorithms.
          </li>
</ul></div>
<h5>
<a name="boost_regex.syntax.basic_syntax.h3"></a>
        <span class="phrase"><a name="boost_regex.syntax.basic_syntax.anchors"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.anchors">Anchors:</a>
      </h5>
<p>
        A '^' character shall match the start of a line when used as the first character
        of an expression, or the first character of a sub-expression.
      </p>
<p>
        A '$' character shall match the end of a line when used as the last character
        of an expression, or the last character of a sub-expression.
      </p>
<h5>
<a name="boost_regex.syntax.basic_syntax.h4"></a>
        <span class="phrase"><a name="boost_regex.syntax.basic_syntax.marked_sub_expressions"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.marked_sub_expressions">Marked sub-expressions:</a>
      </h5>
<p>
        A section beginning <code class="computeroutput"><span class="special">\(</span></code> and ending
        <code class="computeroutput"><span class="special">\)</span></code> acts as a marked sub-expression.
        Whatever matched the sub-expression is split out in a separate field by the
        matching algorithms. Marked sub-expressions can also repeated, or referred-to
        by a back-reference.
      </p>
<h5>
<a name="boost_regex.syntax.basic_syntax.h5"></a>
        <span class="phrase"><a name="boost_regex.syntax.basic_syntax.repeats"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.repeats">Repeats:</a>
      </h5>
<p>
        Any atom (a single character, a marked sub-expression, or a character class)
        can be repeated with the * operator.
      </p>
<p>
        For example <code class="computeroutput"><span class="identifier">a</span><span class="special">*</span></code>
        will match any number of letter a's repeated zero or more times (an atom
        repeated zero times matches an empty string), so the expression <code class="computeroutput"><span class="identifier">a</span><span class="special">*</span><span class="identifier">b</span></code>
        will match any of the following:
      </p>
<pre class="programlisting">b
ab
aaaaaaaab
</pre>
<p>
        An atom can also be repeated with a bounded repeat:
      </p>
<p>
        <code class="computeroutput"><span class="identifier">a</span><span class="special">\{</span><span class="identifier">n</span><span class="special">\}</span></code> Matches
        'a' repeated exactly n times.
      </p>
<p>
        <code class="computeroutput"><span class="identifier">a</span><span class="special">\{</span><span class="identifier">n</span><span class="special">,\}</span></code> Matches
        'a' repeated n or more times.
      </p>
<p>
        <code class="computeroutput"><span class="identifier">a</span><span class="special">\{</span><span class="identifier">n</span><span class="special">,</span> <span class="identifier">m</span><span class="special">\}</span></code> Matches 'a' repeated between n and m times
        inclusive.
      </p>
<p>
        For example:
      </p>
<pre class="programlisting">^a{2,3}$</pre>
<p>
        Will match either of:
      </p>
<pre class="programlisting">aa
aaa
</pre>
<p>
        But neither of:
      </p>
<pre class="programlisting">a
aaaa
</pre>
<p>
        It is an error to use a repeat operator, if the preceding construct can not
        be repeated, for example:
      </p>
<pre class="programlisting">a(*)</pre>
<p>
        Will raise an error, as there is nothing for the * operator to be applied
        to.
      </p>
<h5>
<a name="boost_regex.syntax.basic_syntax.h6"></a>
        <span class="phrase"><a name="boost_regex.syntax.basic_syntax.back_references"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.back_references">Back
        references:</a>
      </h5>
<p>
        An escape character followed by a digit <span class="emphasis"><em>n</em></span>, where <span class="emphasis"><em>n</em></span>
        is in the range 1-9, matches the same string that was matched by sub-expression
        <span class="emphasis"><em>n</em></span>. For example the expression:
      </p>
<pre class="programlisting">^\(a*\)[^a]*\1$</pre>
<p>
        Will match the string:
      </p>
<pre class="programlisting">aaabbaaa</pre>
<p>
        But not the string:
      </p>
<pre class="programlisting">aaabba</pre>
<h5>
<a name="boost_regex.syntax.basic_syntax.h7"></a>
        <span class="phrase"><a name="boost_regex.syntax.basic_syntax.character_sets"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.character_sets">Character
        sets:</a>
      </h5>
<p>
        A character set is a bracket-expression starting with <code class="literal">[</code>
        and ending with <code class="literal">]</code>, it defines a set of characters, and
        matches any single character that is a member of that set.
      </p>
<p>
        A bracket expression may contain any combination of the following:
      </p>
<h6>
<a name="boost_regex.syntax.basic_syntax.h8"></a>
        <span class="phrase"><a name="boost_regex.syntax.basic_syntax.single_characters"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.single_characters">Single
        characters:</a>
      </h6>
<p>
        For example <code class="computeroutput"><span class="special">[</span><span class="identifier">abc</span><span class="special">]</span></code>, will match any of the characters 'a', 'b',
        or 'c'.
      </p>
<h6>
<a name="boost_regex.syntax.basic_syntax.h9"></a>
        <span class="phrase"><a name="boost_regex.syntax.basic_syntax.character_ranges"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.character_ranges">Character
        ranges:</a>
      </h6>
<p>
        For example <code class="computeroutput"><span class="special">[</span><span class="identifier">a</span><span class="special">-</span><span class="identifier">c</span><span class="special">]</span></code>
        will match any single character in the range 'a' to 'c'. By default, for
        POSIX-Basic regular expressions, a character <span class="emphasis"><em>x</em></span> is within
        the range <span class="emphasis"><em>y</em></span> to <span class="emphasis"><em>z</em></span>, if it collates
        within that range; this results in locale specific behavior. This behavior
        can be turned off by unsetting the <code class="computeroutput"><span class="identifier">collate</span></code>
        option flag when constructing the regular expression - in which case whether
        a character appears within a range is determined by comparing the code points
        of the characters only.
      </p>
<h6>
<a name="boost_regex.syntax.basic_syntax.h10"></a>
        <span class="phrase"><a name="boost_regex.syntax.basic_syntax.negation"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.negation">Negation:</a>
      </h6>
<p>
        If the bracket-expression begins with the ^ character, then it matches the
        complement of the characters it contains, for example <code class="computeroutput"><span class="special">[^</span><span class="identifier">a</span><span class="special">-</span><span class="identifier">c</span><span class="special">]</span></code> matches any character that is not in the
        range a-c.
      </p>
<h6>
<a name="boost_regex.syntax.basic_syntax.h11"></a>
        <span class="phrase"><a name="boost_regex.syntax.basic_syntax.character_classes"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.character_classes">Character
        classes:</a>
      </h6>
<p>
        An expression of the form <code class="computeroutput"><span class="special">[[:</span><span class="identifier">name</span><span class="special">:]]</span></code>
        matches the named character class "name", for example <code class="computeroutput"><span class="special">[[:</span><span class="identifier">lower</span><span class="special">:]]</span></code> matches any lower case character. See
        <a class="link" href="character_classes.html" title="Character Class Names">character class names</a>.
      </p>
<h6>
<a name="boost_regex.syntax.basic_syntax.h12"></a>
        <span class="phrase"><a name="boost_regex.syntax.basic_syntax.collating_elements"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.collating_elements">Collating
        Elements:</a>
      </h6>
<p>
        An expression of the form <code class="computeroutput"><span class="special">[[.</span><span class="identifier">col</span><span class="special">.]</span></code> matches
        the collating element <span class="emphasis"><em>col</em></span>. A collating element is any
        single character, or any sequence of characters that collates as a single
        unit. Collating elements may also be used as the end point of a range, for
        example: <code class="computeroutput"><span class="special">[[.</span><span class="identifier">ae</span><span class="special">.]-</span><span class="identifier">c</span><span class="special">]</span></code>
        matches the character sequence "ae", plus any single character
        in the range "ae"-c, assuming that "ae" is treated as
        a single collating element in the current locale.
      </p>
<p>
        Collating elements may be used in place of escapes (which are not normally
        allowed inside character sets), for example <code class="computeroutput"><span class="special">[[.^.]</span><span class="identifier">abc</span><span class="special">]</span></code> would
        match either one of the characters 'abc^'.
      </p>
<p>
        As an extension, a collating element may also be specified via its symbolic
        name, for example:
      </p>
<pre class="programlisting">[[.NUL.]]</pre>
<p>
        matches a 'NUL' character. See <a class="link" href="collating_names.html" title="Collating Names">collating
        element names</a>.
      </p>
<h6>
<a name="boost_regex.syntax.basic_syntax.h13"></a>
        <span class="phrase"><a name="boost_regex.syntax.basic_syntax.equivalence_classes"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.equivalence_classes">Equivalence
        classes:</a>
      </h6>
<p>
        An expression of the form <code class="computeroutput"><span class="special">[[=</span><span class="identifier">col</span><span class="special">=]]</span></code>,
        matches any character or collating element whose primary sort key is the
        same as that for collating element <span class="emphasis"><em>col</em></span>, as with collating
        elements the name <span class="emphasis"><em>col</em></span> may be a <a class="link" href="collating_names.html" title="Collating Names">collating
        symbolic name</a>. A primary sort key is one that ignores case, accentation,
        or locale-specific tailorings; so for example <code class="computeroutput"><span class="special">[[=</span><span class="identifier">a</span><span class="special">=]]</span></code> matches
        any of the characters: a, À, Á, Â, Ã, Ä, Å, A, à, á, â, ã, ä and å. Unfortunately implementation
        of this is reliant on the platform's collation and localisation support;
        this feature can not be relied upon to work portably across all platforms,
        or even all locales on one platform.
      </p>
<h6>
<a name="boost_regex.syntax.basic_syntax.h14"></a>
        <span class="phrase"><a name="boost_regex.syntax.basic_syntax.combinations"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.combinations">Combinations:</a>
      </h6>
<p>
        All of the above can be combined in one character set declaration, for example:
        <code class="computeroutput"><span class="special">[[:</span><span class="identifier">digit</span><span class="special">:]</span><span class="identifier">a</span><span class="special">-</span><span class="identifier">c</span><span class="special">[.</span><span class="identifier">NUL</span><span class="special">.]].</span></code>
      </p>
<h5>
<a name="boost_regex.syntax.basic_syntax.h15"></a>
        <span class="phrase"><a name="boost_regex.syntax.basic_syntax.escapes"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.escapes">Escapes</a>
      </h5>
<p>
        With the exception of the escape sequences \{, \}, \(, and \), which are
        documented above, an escape followed by any character matches that character.
        This can be used to make the special characters
      </p>
<pre class="programlisting">.[\*^$</pre>
<p>
        "ordinary". Note that the escape character loses its special meaning
        inside a character set, so <code class="computeroutput"><span class="special">[\^]</span></code>
        will match either a literal '\' or a '^'.
      </p>
<h4>
<a name="boost_regex.syntax.basic_syntax.h16"></a>
        <span class="phrase"><a name="boost_regex.syntax.basic_syntax.what_gets_matched"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.what_gets_matched">What
        Gets Matched</a>
      </h4>
<p>
        When there is more that one way to match a regular expression, the "best"
        possible match is obtained using the <a class="link" href="leftmost_longest_rule.html" title="The Leftmost Longest Rule">leftmost-longest
        rule</a>.
      </p>
<h4>
<a name="boost_regex.syntax.basic_syntax.h17"></a>
        <span class="phrase"><a name="boost_regex.syntax.basic_syntax.variations"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.variations">Variations</a>
      </h4>
<a name="boost_regex.grep_syntax"></a><h5>
<a name="boost_regex.syntax.basic_syntax.h18"></a>
        <span class="phrase"><a name="boost_regex.syntax.basic_syntax.grep"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.grep">Grep</a>
      </h5>
<p>
        When an expression is compiled with the flag <code class="computeroutput"><span class="identifier">grep</span></code>
        set, then the expression is treated as a newline separated list of <a class="link" href="basic_syntax.html#boost_regex.posix_basic">POSIX-Basic expressions</a>, a match
        is found if any of the expressions in the list match, for example:
      </p>
<pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">regex</span> <span class="identifier">e</span><span class="special">(</span><span class="string">"abc\ndef"</span><span class="special">,</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">regex</span><span class="special">::</span><span class="identifier">grep</span><span class="special">);</span>
</pre>
<p>
        will match either of the <a class="link" href="basic_syntax.html#boost_regex.posix_basic">POSIX-Basic
        expressions</a> "abc" or "def".
      </p>
<p>
        As its name suggests, this behavior is consistent with the Unix utility grep.
      </p>
<h5>
<a name="boost_regex.syntax.basic_syntax.h19"></a>
        <span class="phrase"><a name="boost_regex.syntax.basic_syntax.emacs"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.emacs">emacs</a>
      </h5>
<p>
        In addition to the <a class="link" href="basic_syntax.html#boost_regex.posix_basic">POSIX-Basic features</a>
        the following characters are also special:
      </p>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
                <p>
                  Character
                </p>
              </th>
<th>
                <p>
                  Description
                </p>
              </th>
</tr></thead>
<tbody>
<tr>
<td>
                <p>
                  +
                </p>
              </td>
<td>
                <p>
                  repeats the preceding atom one or more times.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  ?
                </p>
              </td>
<td>
                <p>
                  repeats the preceding atom zero or one times.
                </p>
              </td>
</tr>
<tr>
<td>
                <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
                      ?
                    </li></ul></div>
              </td>
<td>
                <p>
                  A non-greedy version of *.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  +?
                </p>
              </td>
<td>
                <p>
                  A non-greedy version of +.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  ??
                </p>
              </td>
<td>
                <p>
                  A non-greedy version of ?.
                </p>
              </td>
</tr>
</tbody>
</table></div>
<p>
        And the following escape sequences are also recognised:
      </p>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
</colgroup>
<thead><tr>
<th>
                <p>
                  Escape
                </p>
              </th>
<th>
                <p>
                  Description
                </p>
              </th>
</tr></thead>
<tbody>
<tr>
<td>
                <p>
                  \|
                </p>
              </td>
<td>
                <p>
                  specifies an alternative.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  \(?: ... )
                </p>
              </td>
<td>
                <p>
                  is a non-marking grouping construct - allows you to lexically group
                  something without spitting out an extra sub-expression.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  \w
                </p>
              </td>
<td>
                <p>
                  matches any word character.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  \W
                </p>
              </td>
<td>
                <p>
                  matches any non-word character.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  \sx
                </p>
              </td>
<td>
                <p>
                  matches any character in the syntax group x, the following emacs
                  groupings are supported: 's', ' ', '_', 'w', '.', ')', '(', '"',
                  '\'', '&gt;' and '&lt;'. Refer to the emacs docs for details.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  \Sx
                </p>
              </td>
<td>
                <p>
                  matches any character not in the syntax grouping x.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  \c and \C
                </p>
              </td>
<td>
                <p>
                  These are not supported.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  \`
                </p>
              </td>
<td>
                <p>
                  matches zero characters only at the start of a buffer (or string
                  being matched).
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  \'
                </p>
              </td>
<td>
                <p>
                  matches zero characters only at the end of a buffer (or string
                  being matched).
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  \b
                </p>
              </td>
<td>
                <p>
                  matches zero characters at a word boundary.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  \B
                </p>
              </td>
<td>
                <p>
                  matches zero characters, not at a word boundary.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  \&lt;
                </p>
              </td>
<td>
                <p>
                  matches zero characters only at the start of a word.
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  \&gt;
                </p>
              </td>
<td>
                <p>
                  matches zero characters only at the end of a word.
                </p>
              </td>
</tr>
</tbody>
</table></div>
<p>
        Finally, you should note that emacs style regular expressions are matched
        according to the <a class="link" href="perl_syntax.html#boost_regex.syntax.perl_syntax.what_gets_matched">Perl
        "depth first search" rules</a>. Emacs expressions are matched
        this way because they contain Perl-like extensions, that do not interact
        well with the <a class="link" href="leftmost_longest_rule.html" title="The Leftmost Longest Rule">POSIX-style
        leftmost-longest rule</a>.
      </p>
<h4>
<a name="boost_regex.syntax.basic_syntax.h20"></a>
        <span class="phrase"><a name="boost_regex.syntax.basic_syntax.options"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.options">Options</a>
      </h4>
<p>
        There are a <a class="link" href="../ref/syntax_option_type/syntax_option_type_basic.html" title="Options for POSIX Basic Regular Expressions">variety
        of flags</a> that may be combined with the <code class="computeroutput"><span class="identifier">basic</span></code>
        and <code class="computeroutput"><span class="identifier">grep</span></code> options when constructing
        the regular expression, in particular note that the <a class="link" href="../ref/syntax_option_type/syntax_option_type_basic.html" title="Options for POSIX Basic Regular Expressions"><code class="computeroutput"><span class="identifier">newline_alt</span></code>, <code class="computeroutput"><span class="identifier">no_char_classes</span></code>,
        <code class="computeroutput"><span class="identifier">no</span><span class="special">-</span><span class="identifier">intervals</span></code>, <code class="computeroutput"><span class="identifier">bk_plus_qm</span></code>
        and <code class="computeroutput"><span class="identifier">bk_plus_vbar</span></code></a> options
        all alter the syntax, while the <a class="link" href="../ref/syntax_option_type/syntax_option_type_basic.html" title="Options for POSIX Basic Regular Expressions"><code class="computeroutput"><span class="identifier">collate</span></code> and <code class="computeroutput"><span class="identifier">icase</span></code>
        options</a> modify how the case and locale sensitivity are to be applied.
      </p>
<h4>
<a name="boost_regex.syntax.basic_syntax.h21"></a>
        <span class="phrase"><a name="boost_regex.syntax.basic_syntax.references"></a></span><a class="link" href="basic_syntax.html#boost_regex.syntax.basic_syntax.references">References</a>
      </h4>
<p>
        <a href="http://www.opengroup.org/onlinepubs/000095399/basedefs/xbd_chap09.html" target="_top">IEEE
        Std 1003.1-2001, Portable Operating System Interface (POSIX ), Base Definitions
        and Headers, Section 9, Regular Expressions (FWD.1).</a>
      </p>
<p>
        <a href="http://www.opengroup.org/onlinepubs/000095399/utilities/grep.html" target="_top">IEEE
        Std 1003.1-2001, Portable Operating System Interface (POSIX ), Shells and
        Utilities, Section 4, Utilities, grep (FWD.1).</a>
      </p>
<p>
        <a href="http://www.gnu.org/software/emacs/" target="_top">Emacs Version 21.3.</a>
      </p>
</div>
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
<td align="left"></td>
<td align="right"><div class="copyright-footer">Copyright © 1998-2013 John Maddock<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
      </p>
</div></td>
</tr></table>
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